Method of making crank shafts



31, 1932- E. T. cAussh v 1,860,607

METHOD OF MAKING CRANK slur-Ts Filed April 15, 1929 17 17 Z4 L A 7lNVENTOR 2 izwz two parts.

Patented May 31, 1932 V UNITED 's'm'ras PATENT OFFICE 7 EDWARD '1. CAUSE'R, OF BEAVER FALLS, IENNSYLVANIA, ASSIGNOR TO UNION DRAWN.

STEEL COMPANY, OF BEAVER PENNSYLVANIA, A CORPORATION OF PENN- SYLVANIA .EETHOD OF MAKING CRANK HAFTS Application filed April 15,

This invention relates to a method of making crank shafts for internal combustion engines, and. is particularly applicable to crank shafts. for radial cylinder engines of the type I commonly employed as airplane motors.

The design of many airplane motors necessitates the crankshaft being made intwo separate pieces to facilitate the assembling of the engine. Heretofore, these parts have 10 been made separately, as separate forgings,

and machined separately. This requires two complete sets of forging dies, two distinct machiningfoperations, one for each part, and finally the fitting together of the According to the present invention, it is proposed to make the crank shaft as a onepiece forging, perform various machining operations thereon, and finally separate the forging at a predetermined point to provide the separate parts.

The invention may be readily understood by reference to the accompanying drawings which illustrate my invention and in which,

Figure 1 is a side elevation of the completed front end portion of the crank shaft assembly;

Figure 2 is a similar view of the rear end.

portion of the crank shaft assembly; and

Figure 3 is a side elevation of the one-piece forging from which the two parts shown in Figures 1 and 2 are obtained.

The parts shown in Figures 1 and 2 are the conventional parts of the crank shaft fully machined and ready for assembly. The front end member comprises a shaft portion 2 which mustbe machined and having an extension 3 of reduced diameter which must also be accurately machined and in which key slots are cut to retain a propeller. Beyond the reduced portion 3 is a threaded portion 4.

At the other end of the shaft 2 is a cross portion or check 5 on which is an eccentric crank pin 6. Opposite the crank pin 6 is a counterweight 7 The crank pin 6 has a re duced portion 6' adapted to be received in an opening 8 in the rear end member 9 shown in Figure 2, this rear end member 9 having a cheek portion 10 corresponding in shape to the cheek portion 5 of the'front end member,

and the hole 8 is eccentrically ositioned in the cheek portion 10. The mom er 9 is counterweighted at 11. It has a hub portion 12 which is. machined externally. Both the front end member and the rear end member have, an internal bore, as indicated in dotted lines in the drawings. a

As heretofore made, the front end member I and the rear end member have been forged separately and machined separately, necessitating separate forging dies for each memher and necessitating a series of separate machining operations for each of the two members.

According to the present invention, a crank shaft is forged in one piece, as shown in Figure 3, the front end portion and the rear end portion being connected by the crank pin, which is originally made longer than is necessary for the crank pin in the finished assembly. In Figure 3, the one-piece forging 15.

has a crank pin portion 16, cheeks 17 with counterweights 18. One of the cheeks has a forwardly extending shaft ortion 19, and on the other cheek portlon is a ub portion 20.

. In carrying out the present invention, the crank shaft forging is machined. U on setting the forging u vin-a lathe, or ot er ma? chine toolto turn it out its main longitudinal axis A-A, the necessary machining of the extension 19 can be effected to provide the portion 2 of Figure 1, the portion 3 and the threaded portion 4 and at the same time the hub portion 20 can be turned down to come 0nd to the portion 12 of Figure 2. Both t e rear end portion and. front end portion can be internally machined or bored at the same setting.

The one-piece unit may then be turned,

nring the A ting through the crank pin substantially in the plane of line CC,the crank pin having originally been forged lon enough to permit of it being severed in this manner. After the forging has been severed, the hole 8 can be formed in that piece that forms the rear end section and the two parts are complete.

The process possesses many advantages in that it eliminates the separate handling of the different pieces the separate setting up of the pieces for t e various machining operations, provides for multiple tooling operations, and reduces the chance of spoilage because the two parts, bein made as one, will fit accuratel Y together a ter they have been separated. cing made in one piece and be ing machined at one time, the parts will fit together with greater accurac than can be obtained in the manufacture 0 the parts separately.

The process also considerably reduced the labor cost through the elimination of the handlin of the separate parts and the time lost in the setting up of the separate parts in the machine tools.

Furthermore, the crank shaft itself is a superior product because, being forged as a sin le piece, it has a uniform metal content an the grain structure is developed, particularly 1n the crank pin, under more favorable conditions than where the two parts are forged separately. The assembly is also superior for the reason that the two parts, being made as a unit and machined as a unit, fit together with greater accuracy than where the parts are made separately.

It will be understood. that in the drawings the crank shaft has been shown in a more or less conventional fashion and that the invention is not confined to the particular construction and shape therein illustrated, the drawings being merely for the purpose of illustration. It will also be understood that various parts may be differently machined according to the design and construction of the particular crank shaft and that the invention is not to be considered as restricted to the manufacture of the particular construction herein shown and described, but may be utilized inthe manufacture of crank shafts of various types.

I claim: 1. The method of manufacturing a twoiece crank shaft assembly which comprises orming the two parts of the crank shaft having a crank pin disposed between the two parts as a rigid integral forging, machining oth parts of the forging as a unit, and then severing the crank pin to provide the separate parts.

2. In the manufacture of a two-piece crank shaft assembly in which both pieces have a check portion and a hub portion and in which one piece has a crank pin adapted to engage a socket in the cheek portion of the other, the steps which com rise forging both parts and a connecting pin etween the parts as a single unit, machining both parts as a single unit, severing arts and then further machining one part for cooperation with the other.

3. In the method of forming a two-piece crank shaft assembly wherein each part has a cheek portion and a hub portion, the steps which comprise forming the two parts as a single unit connected by a-crank pin portion of a dimension longer than the crank pin of the finished assembly, machining the one-piece unit, and then separating the unit by cutting across the crank pin portion thereof closely adjacent the cheek of one part whereby substantially the full length of the crank pin remains attached to the other part, and thereafter forming a socket in the check portion of the part from which the pin has been severed and in line with the former axis of the pin.

4. The process of manufacturing a crank shaft assembl having a front end portion and a rear en portion which comprises initially forming both portions in a single unit connected by a crank pin portion whose dimension is lon er than the crank pin of the finished assembly, and then separating the two portions by severing the crank pin adjacent one end thereof so that the greater portion of the crank pin is on one portion, and thereafter removin the remnant of the crank pin portion from tl ie other member and providing a socket therein in line with the former axis of the crank pin, said socket being adapted to receive the end of the crank pin of the other member.

In testimony whereof I have hereunto set my hand.

EDWARD T. CAUSER.

the connecting pin to provide two 

